Some devices not working or synching on wifi

Hi,
I have an issue with some of the devices on my Utility Warehouse wifi network and can not access the Internet or sync with an email server? I have run a WiFi checker and everything seems fine. Using mobile data works fine with all devices. I have eero and wavelink WiFi extenders, a technicolor router and a wired smart TV (which is fine).
Has anyone got any idea what issue is?

Many thanks, Neil

Not much info.

What devices, how are you connecting those devices?

Firstly try connecting to the modem/router (Technicolor) only and see if you can connect.

Work forward from there.

Which device types aren't working? Include OSes and versions if possible.

Have they worked on any other wifi previously? As you have multiple vendor WIFI Extenders, have you checked that theres no DHCP loop (so more than one wifi extender is giving out IP addresses - or the wrong Default Gateway?)

I have no experience of those particular extenders, but usually this is checked on the web interface/accompanying application.

Can you wire-in a laptop direct to the router and check internet access is OK?

If you switch off all of your extenders, and then move a non-working wifi device into range of the Technicolor, does it work?

You've basically said what I did 2 days earlier.